Teach RenameThread to work on OSX

src/util.cpp

@@ -1287,6 +1287,8 @@ void RenameThread(const char* name)
     //       on FreeBSD or OpenBSD first. When verified the '0 &&' part can be
     //       removed.
     pthread_set_name_np(pthread_self(), name);
+#elif defined(MAC_OSX)
+    pthread_setname_np(name);
 #else
     // Prevent warnings for unused parameters...
     (void)name;